99.5%? Is it possible?

[SapunovDmitry]

Yeah. I think it is possible to refine for 99,5% but only if you buy refined gold from tho owner.
There is a trick in Russia. If you buy gold from the bank you pay 18% tax. If you refine gold you pay NOT FOR GOLD but for GOLD IN GOLD BEARING SCRAP and this is a different story and you get it without paying this tax. And if you make rings or spoons or whatever from that gold you have most of your profit on jewelery operation.

I don't know but i think in US the situation is kind of the same, because of those people who buy gold from ebay over the spot.

 

[4metals]

After gassing with SO2 the PGM's were cemented with copper. Back in the '80's during the last gold scrap rush, there was considerable platinum and palladium and iridium in the waste. To recover these metals cementing was necessary. The solution was treated with MagOx to raise the pH to drop out any remaining metals and the solids were filter pressed and the liquids discharged as they met the sewage discharge criterion.

Filtration was by a 50 cm table top buchner funnel. The filter media was actually in the form of pads which were rigid and about 1/4 inch thick. They fit tightly into the funnel bottom and swelled when wet. These pads filtered the material both quickly and to a small micron porosity.
Back then the pads were about $2 each. When we first used these pads we saved them and burned them to recover any gold but between the strong suction and the fact that the chlorides were rinsed from the pads to process separately, there was never any values in the burnt residues so we stopped burning them.

 

[HAuCl4]

Thanks again 4metals for the thorough descriptions.

You may step down from the expert witness stand!. I'm sure if anyone wants to cross examine you they'll post the questions!.

Seriously, thanks a lot for openly sharing your knowledge. I learned a lot.

You too GSP.

 

[HAuCl4]

I thought I would ask one last question to 4metals:

What would you change in your processes if you had to do it over again today?

 

[4metals]

I would change a lot! The real reason for the chlorine (Miller process) is the speed of getting the product into a high purity. The next step, whether it is aqua regia or electrolytic is still necessary. Aqua regia is faster than electrolytic, one has waste the other ties up gold longer.

In my mind the fix is chemical refining but with a twist. First the karat material needs to be in the proper form physically. Big changes in the refining process can be had by processing a fine 100 to 200 mesh powder. To do that the molten gold has to be atomized. A water atomizer is the most cost effective way to go here. It takes the proper balance of high pressure water hitting a thin stream of gold to get it right but the payoff is big.

If your fine powdered gold scrap is suspended in warm hydrochloric acid and agitated the gold will dissolve with the addition of chlorine. But chlorine is a chore to work with to say the least. A handy substitute is sodium chlorate. Warm hydrochloric, sodium chlorate plus gold (finely divided) will give you Aurochloric acid. From there on out it's simple.

Actually much simpler than you would imagine at first. Since there was no nitric used in the process, there is no nitric to eliminate before precipitation begins, second you can add ammonium chloride after cooling and filtering to recover any platinum. Palladium will come down as well because there is an excess of sodium chlorate in solution. Filter out the Pt and Pd and go for the gold. Fast and easy, no chlorine, no NOx scrubbing. Happy days, isn't chemistry a wonderful thing?

 

[HAuCl4]

Wow. That was really creative!.

You'd actually choose sodium chlorate over NaClO?. Faster, cheaper or both?.

100 mesh is really thin. Have you done it or seen it done?

Would you recycle the HCl at the end?.

 

[Lou]

I would say that I'd only use sodium chlorate or sodium hypochlorite (or chlorine for that matter) if and only if it were substantially silver free gold I was dissolving. It's nice to not have to fret about removing nitrogen oxides and residual nitric acid, especially nice considering you're not producing lots of NOx to go out into the environment. Bear in mind though, adding only just enough nitric is quite easily accomplished with a large equal pressure addition funnel or a diaphragm pump. Cover your gold in conc. HCl, and add in nitric as needed. Some people prefer not to heat while doing gold, but heat is a requirement for platinum.

 

[4metals]

I've never tried to recycle HCl as it is saturated with SO2 after the gold is dropped. Maybe I'm not as green as others. I went for speed of recovering product over recycling.

Actually 200 mesh is attainable with a minimal % oversize and yes I've seen it done and it is done in production levels. This method is used in production methods although its not talked about.

I used sodium chlorate because it has a higher percentage of chlorine available. It is a strong oxidizer and there are precautions involved in its use and storage.

I'd tell you more but then I'd have to hunt you down. :lol:

 

[4metals]

Lou,

I have worked this process successfully with silver as high as 10%. The silver chloride makes an easier job of collecting the undissolved particles which are reduced with the silver chlorides and processed in a cell to recover any slimes.

The encrustation by silver chloride is an issue at 200 mesh but the fine mesh does allow good penetration and the resulting entrapped gold in the silver bar after reduction is similar in concentration to the gold entrapped in aqua regia refining of cornflake karat scrap. Which is usually 1% or less of the assay of the silver bar.

Unless you spend a ton of money on an atomizer (like $250,000) where you can be assured your over-sized is minimal, I assume the over-sized particles are too large for the Cl-HCl reaction to go to completion so they end up in the insolubles and get processed with the chlorides.

I have never sieved the powder and tested this procedure on dust I know to be 200 mesh or smaller to test this theory. It is a pain to dry the powder to sieve it (I suppose I could sieve it wet) and as the gold levels in the insolubles aren't too high I haven't taken the time to do a proper test. (Something for my to do list)

The biggest problem is waiting for the fine mesh powders to settle in the atomizing tank, currently it is filtered but I'm up for suggestions.

 

[HAuCl4]

Lou,

IThe biggest problem is waiting for the fine mesh powders to settle in the atomizing tank, currently it is filtered but I'm up for suggestions.

A vibrating tank perhaps will help settle faster?.

Not planning anything, as this is just an intellectual pursuit for me. Great ideas and variations nonetheless!.

 

[4metals]

Was able to sift some atomized powders last week to quantify the sizes before digestion, the HCl sodium chlorate reaction goes to completion on particles as large as -50 mesh. This process is also effective on material containing up to 20% silver. The small particle size allows the acid to penetrate completely and the resultant chlorides contain only traces of gold, not the typical 1% found by digesting typical karat (8%Ag) which has been corn-flaked and digested in aqua regia.

 

[HAuCl4]

Digestion must be very fast too. They are going to call you the flash refiner!. 8)

I bet the atomizer is not too easy to build.

 

[nickvc]

Was able to sift some atomized powders last week to quantify the sizes before digestion, the HCl sodium chlorate reaction goes to completion on particles as large as -50 mesh. This process is also effective on material containing up to 20% silver. The small particle size allows the acid to penetrate completely and the resultant chlorides contain only traces of gold, not the typical 1% found by digesting typical karat (8%Ag) which has been corn-flaked and digested in aqua regia.

This is fascinating if I remember we had a member that was using water jets to do the same process on his dental scraps, this will speed up the time that the high values are left lying around expotentialy and produce high grade gold if the processing is done properly, it almost makes the Miller Process redundant. Keep the research going it's got great potential for large scale refining.

 

[Irons]

Digestion must be very fast too. They are going to call you the flash refiner!. 8)

I bet the atomizer is not too easy to build.

I wonder how a modified power sprayer would work.

 

[HAuCl4]

Digestion must be very fast too. They are going to call you the flash refiner!. 8)

I bet the atomizer is not too easy to build.

I wonder how a modified power sprayer would work.

:shock:

Why am I getting the drift that you have been joking with me for a while Irons?. :lol:

 

[Barren Realms 007]

Digestion must be very fast too. They are going to call you the flash refiner!. 8)

I bet the atomizer is not too easy to build.

I wonder how a modified power sprayer would work.

:shock:

Why am I getting the drift that you have been joking with me for a while Irons?. :lol:

I don't think he was, there was a thread on here about atomizing gold to digest it faster. The pressure of the water was around 2,500-3,000 PSI or higher that was used.

 

[4metals]

The pressure does come from a pressure washer, it,s the modifications to make the pressure consistent that's the hard part. The basic atomizer, which can process 500 pounds per hour (that's 7,291 ounces) costs $150,000 without the melter.

 

[HAuCl4]

That digestion must take ... 30 minutes tops?.

One could make the pressure consistent with an hydraulic capacitor. Basically a high pressure air and water tank. The exact design of the (heated ceramic? ) metal nozzle is likely the most high-tech part.

El CheapO would stick with inquartation first and avoid atomizers, with a good nitric-recycle plan. Still would get the job done within an 8 hour shift, and maybe better accounting for all 4 metals and insolubles. I think. :?: :idea:

 

[goldenchild]

It comes down to a question of scale, aqua regia refining in large enough lot sizes, costs a medium sized refiner about 1/4 of 1% for labor chemicals treatment of waste etc. Assuming your process yields 99.875 accountability on lot by lot basis and the balance is retrieved from residues, slags, baghouse dust, etc. This says nothing of insurance, security and overhead.

So if you process a Phaudler full of karat you can still make a profit at 1/2%. But there is no room for error. Those rates are for the big refiners and only given on larger lots. So if you're not dealing with JM Branford, Metalor' Republic, or Ohio precious metals, watch your back.

4metals,

What is the significance of the number 99.875? The last time I had my gold assayed thats what the purity came out to be.

 

[Barren Realms 007]

It comes down to a question of scale, aqua regia refining in large enough lot sizes, costs a medium sized refiner about 1/4 of 1% for labor chemicals treatment of waste etc. Assuming your process yields 99.875 accountability on lot by lot basis and the balance is retrieved from residues, slags, baghouse dust, etc. This says nothing of insurance, security and overhead.

So if you process a Phaudler full of karat you can still make a profit at 1/2%. But there is no room for error. Those rates are for the big refiners and only given on larger lots. So if you're not dealing with JM Branford, Metalor' Republic, or Ohio precious metals, watch your back.

4metals,

What is the significance of the number 99.875? The last time I had my gold assayed thats what the purity came out to be.

That is how pure your button is the balance to .9999 in the figure is the impurities you had in it.